class_docstr: Class for the Hitting Set Algorithm to obtain a approximate minimal set of backdoor variables
  to condition on for each node pair.
docstr: Find the node contained in most number of sets.
docstr_tok: ["Find","the","node","contained","in","most","number","of","sets","."]
code: def _max_occurence_var(self, var_dict):
      """
      Find the node contained in most number of sets.
      """
      max_el = None
      max_count = 0
      for key, val in var_dict.items():
          if val > max_count:
              max_count = val
              max_el = key
      return max_el
  
imports: import networkx
  from dowhy.utils.graph_operations import adjacency_matrix_to_adjacency_list
label_desc: Use image node_id 6 for calling the HittingSetAlgorithm obj's underlying member method code with example usage: obj._max_occurence_var(var_dict) and returns: max_el